[ectospheno]

The rebase command is only safe if you never share a branch. Most people use a distributed revision control system to work with others and if you do work with others then rebase is dangerous and should not be used.

Almost every rebase user I've spoken with has no idea what the danger is despite it being clearly discussed in the manual page for rebase and despite rebase being listed as dangerous every time it is mentioned in any manual page.

For the sake of new users everywhere, please stop recommending rebase.

[incog-neato]

This is overly broad dissuasion. `rebase` should not be used if the branch is already shared and built upon by others, but is completely harmless to use on a feature branch.

In fact, it produces cleaner feature branches for review. Tracking the trunk branch with merges into your feature branch makes for a lot of noisy commits and difficult history to read through when the time comes to diagnose a bug. Rebasing, on the other hand, allows you to neatly put all the changes from your branch (and only those changes) into one or a few neatly-packaged commits.

[pierrebai]

Not rebasing does not affect reviewing a branch in the least, unless your diff software is seriously broken.

Comparing a branch to trunk shoudl only shows the actual difference. That you merged trunk multiple times shoudl have zero bearing.

The only way it could ever confuse anyone is if they review every commit and somehow fail to pass over merge commits.

The single most aggravating thing in git are its self-appointed super-users who /almost always/ properly use its power until one day they don't. Then they make life miserable for everyone else while we all "just wait, I'm fixing it".

[palebluedot]

Feature branches really should be rebased to have clean self-contained logical commits prior to merging, and this goes beyond just making it easier to review (although that is an important point). It's good git hygiene!

No individual commit should break the build; one reason is to keep git-bisect working well for future users bug-hunting, without getting stopped because someone didn't keep the commits on their dev branch clean prior to merging (N.B., a maintainer should also reject such PRs). And keeping commits clean usually means needing to rebase occasionally to organize the commits.

And each commit should be reviewed individually, in addition to the whole of the branch / PR.

Not to mention that each commit should be logically laid out, with well-defined changes and well-written commit messages. This usually means needing to rebase a branch when developing non-trivial features or bug fixes, to fold in review feedback.

But as mentioned elsewhere, generally on feature / dev branches, the expectation is that the commits are unstable, subject to change, and should not be built upon (without prior coordination, at least).

Master and stable release branches, on the other hand, should never change or be rebased.

[james-mcelwain]

Absolutely. Personally, I like to spam commits while I'm developing, just to make sure I keep track of what I've done while I'm iterating, but none of this is relevant to the final merge. Any individual commit on my feature branch may not even compile, but when that feature is applied to master, I want it to be a clean atomic commit that can easily be reverted or applied to other branches.

[incog-neato]

There are 2 things I dispute here:

1. I didn't say this affects branch diffing, but rather trawling through history on a single branch.

2. "self-appointed super-users [...] [who break everything]" is a strawman and borderline ad-hominem. If you follow the guidelines I put forth, there won't be any issues collaborating with others.

Also, as a general note, it's actually very difficult to completely destroy information that's been committed at some point. If you're really running into issues with this, don't let fear direct you away from enjoying the greatest features of git. Experiment! Keep trying. Read a good git book (https://git-scm.com/book/en/v2). And learn to use the reflog. Everything you've committed is backed up for a long time even if you've removed all named references to those commits.

[V-2]

> I didn't say this affects branch diffing, but rather trawling through history on a single branch.

Exactly. What's the point of all the "oops, a typo" or "applying code review remarks, part III" commits. Just rewrite. This is the workflow you get eg. with Gerrit.

[convolvatron]

choosing between readable commits and mergeable history is a false dichotomy - just because git imposes that choice doesn't mean its fundamental

[slavik81]

Merge commits can contain changes not included in any parent commits. You can't just ignore them.

[anyzen]

I strongly disagree. Git rebase is a very useful command, but of course you need to know what you are doing. Git becomes very weird if you try to avoid its core concepts... as far as I'm concerned, use rebase, get yourself cut (or better yet, learn about it before using it) and try not to repeat mistakes.

That said, git porcelain is simply awful. It is inconsistent and full of dangers - there is no way I would dare try new commands without reading up on them, because the names are often misleading. Sometimes I really wish GitHub / GitLab used Mercurial as their foundation. I think the world of programming would be much easier....

[linkmotif]

This is exactly what I'm talking about! Thank you!

There is /nothing/ "dangerous" about rebasing. You just don't rebase branches that are publicly shared without coordinating with the other users, so for some cases (like "master" of an open source project) you don't rebase.

But for your internal workflow, rebase is a KEY TOOL. It's how you write your story of commits. You can't just perfectly nail your commit history the first time you code, unless you are a genius. And what if you're working on a feature, but then you want to commit a certain series chunk of changes to master, so that other features can use that change. Rebase is how you do anything like this. It's core to using and enjoying the beauty of git.

Not to mention reset...

[shandor]

Rebase is not dangerous. It can't be, since it only works on the local repo.

It's non-fast-forward pushes that are dangerous. And they're dangerous whether anyone uses rebase or not.

[collinmanderson]

Exactly, it's the force pushes that are the problem.

[pjc50]

Loss of un-pushed work can be an issue, which I think is the thing that makes people wary.

[palebluedot]

Almost always, you can recover a bad rebase via git reflog.

[pjc50]

That's true, but it's an obscure feature, not a convenient "undo" button; to the average insecure git user you might as well tell them that their work has been eaten by a dragon and they can recruit another dragon to get it back.

[GhostVII]

Reflog may not be known by the average git user, but I think it is pretty convenient - just call `git reflog`, copy the hash before the rebase, and checkout/reset to that hash. Doesn't get much easier than that.

[stouset]

I rebase pushed branches all the time if I’m the only one who is working on them, even for repos with multiple team members working on them. In almost a decade I can’t think of a single time this has caused problems.

Yes, don’t rebase branches with multiple authors doing parallel work. But I can’t think of many times I’ve even had to work on a feature branch with multiple authors.

[pjc50]

Rebase is context-dependent.

In a gerrit flow, you have to use it quite often, but only on the detached micro-branches that gerrit forces you to use. And the UI provides a nice convenient rebase button.

In a more traditional "trunk" flow, where you're pretending it's svn, you probably want "pull.rebase=true", otherwise you generate a lot of entirely spurious merge commits. This really confused me the first time I used git, long ago.

The "dangerous" case is, as you say, using it to rewrite history that has already been pushed (heresy!). Generally the system will warn you that this requires "--force", at which point you need to stop and think about what you've done.

(It took me a long time to overcome my feeling that history rewrites were inherently wrong - defeating the point of a VCS in some way. I've adapted to it somewhat with the "neatening things up before submitting" view, which took a while to learn. In a traditional VCS there's only one view of the code and everyone shares it.)

[camgunz]

In a lot of workflows I've used, we _always_ rebase against <parent branch> before pushing a PR, the virtue being that the history is cleaner. I definitely don't think it deserves the huge "NEVER USE" sticker you're slapping on it. I use it multiple times a day.

[hnrodey]

False.